Before we jump from one horse to the other, we need to look at the horse we want to ride.According to Donald Johanson (Remember, Lucy?), the Multiregional Continuity model (MRH) has the following characteristics.

The Multiregional Continuity Model15 contends that after Homo erectus left Africa and dispersed into other portions of the Old World, regional populations slowly evolved into modern humans. This model contains the following components:

some level of gene flow between geographically separated populations prevented speciation, after the dispersal

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GRM: And the evidence for this gene flow lies in our nuclear genome. People seem to forget that the mtDNA tells only 16000/3,200,000,000ths = 1/200,000 of the story of human genetic history. I list several evidences for the ancient genetic flow on http://home.entouch.net/dmd/hegene.htm The coalescence time is an indication of the amount of connection we have in a particular gene to our ancestors.

>>>>all living humans derive from the species Homo erectus that left Africa nearly two million-years-ago

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That is true regardless of whether or not one is an OOA or multiregionalist. Some of the nuclear genetic evidence (remember that source has 200,000 times more information than the mtDNA does) says that there was indeed back migration from the H erectines from Asia back to Africa and we carry some of those genes. Unfortunately, I am in Boston without my database so I can't cite you the work, but if you are interested when I get back to Beijing, I can provide it.

>>>>natural selection in regional populations, ever since their original dispersal, is responsible for the regional variants (sometimes called races) we see today <<<

Asians have a unique type of tooth, called sinodont. It is a shovel shaped tooth. I have not checked to see if my granddaughters (both of whom ultimately have ancestry back to Asia) have those type of teeth or not. The amazing thing is that is always ignored by replacement people is that Peking Man also had those shovel shaped teeth. So, ooA requires that we believe that merely living near Beijing causes your teeth to be shovel-shaped. Isn't a simple explanation to be found in genetic descent? As to Europeans, they continue to show (in very small minorities) traits which were found in the archaic Neanderthals who were supposedly totally replaced. Does merely living in Europe cause these different traits to arise? here is the data

Here is some data on the Nasion. The African Eves and Skhul/Qafzeh peoples are the African invaders who were supposed to replace all previous humans on the planet. But notice the have a low nasion index but the earliest Eueopeans move in the direction of the Neanderthals. This is evidence of hybridization:

And the strongest piece of information is the H-O form of the mandibular foramen (the place the dentist tries to shoot novacaine). ONly Neanderthals had this form. It was not found in AFrica, yet, a significant minority of the earliest anatomically modern Europeans have the H-O form of the foramen.

Then there is Melanocortin -1 which is the red hair gene. It arose in Europe 100,000 years ago, not in Africa and it does have some protection from the cold something the Africans were unlikely to need but Neanderthals would have. In Europe, 100kyr ago, there were only Neanderthals.

>>>>the emergence of Homo sapiens was not restricted to any one area, but was a phenomenon that occurred throughout the entire geographic range where humans lived

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Dick, this is the one I disagree with. It views humanity as one continuously evolving single species. It isn't like humans arose here and there independently.

>>>>>Now the counter intuitive part is the idea that H erectus in Europe and H erectus in Africa developed in situ to become H sapiens in both locations.This would be like putting zebras in Australia and zebras in Africa and a million years later finding horses grazing on both continents with only fossils of zebras to be found.And this ignores the second wave out of Africa that occurred around 100,000 years ago with both displacement and interbreeding combined.<<<

You know, Siberian tigers are capable of breeding with indian Tigers who are capable of breeding with lions to create the liger. Your amazement at this happening with humanity when it happens with other long separated creatures is amazing in and of itself.